The study found that, contrary to popular belief, sex and nudity failed to positively affect a film's popularity among viewers or critics and did not guarantee big box office receipts.

One of the study's co-authors, Dean Keith Simonton, said theirs was the largest sample of its kind used for film research. The results surprised him, he said.

"Sex did not sell, whether in the domestic or international box office, and even after controlling for MPAA rating," said Simonton, who is a professor of psychology at the University of California, Davis. "In other words, even among R movies, less graphic sex is better."

The top-grossing films in the study included movies like "Shrek 2;" "Spider-Man;" "Star Wars Episode III: Revenge of the Sith" and "The Lord of the Rings: The Return of the King," all of which contained mostly minor to mild sex and/or nudity.

Simonton said the research went beyond others in that it also examined other forms of "objectionable" material that might earn a film an R rating including violence.

The study was prompted by an experience almost a decade ago of its co-author, Anemone Cerridwen.

Cerridwen had been taking acting classes and increasingly became uncomfortable with some of the sexualized content she was encountering. That led her to consider the work experiences of film actresses and the pursuit of data about the lucrativeness of sex in movies.

"I assumed sex sold, and wanted to know by how much," Cerridwen said. "I braced myself for the worst, and got quite the surprise."

Craig Detweiler, director of the Center for Entertainment, Media and Culture at Pepperdine University, said the study's findings reflect the culture's post-sexual revolution sensibilities.

"Nothing is as shocking anymore," Detweiler said. "You can see it in Britney Spears' kiss with Madonna and Janet Jackson's Super Bowl performance. Things that were a big controversy among some, the next generation kind of yawned at it."

Rather, Detweiler said, he has seen among his students that the new form of rebellion against the older generation includes "not doing drugs, not sleeping around and not getting divorced." That might explain the popularity of some of the Jane Austen films and movies like the "Twilight" series, he said.

"Those stories are really about sexual separation," he said. "They are all about wooing, not winning."

Tom Jacobs, staff writer for the academic research periodical Miller-McCune, wrote about the study and said there has long been the belief that the many young males who make up movie audiences are enthralled by female nudity.

"These researchers really put that belief to the test and crunched the numbers," Jacob said. "What I took from the study is that a hint of sex is perhaps more enticing than out-and-out nudity."

The study's authors are hopeful that their findings will have some impact on moviemaking.

Simonton said he has had one inquiry from a researcher at a major studio that he declined to name, though he has no idea if the studio plans on acting on the data.

Cerridwen said she thinks movies continue to be influential on the public and believes their study could also have an influence, especially if other academics pick up the torch and continue the research. Until then, she hopes Hollywood takes notice.

"I do believe that there are a fair number of people in the film industry who want to make better films, and this study may give them some ammunition," she said. "I know that Hollywood has been trying to make more family-friendly films for a while (since the '90s) and it seems to be helping ticket sales, so my guess is that this research would complement that."